Re: [PATCH net] sctp: fix copying more bytes than expected in sctp_add_bind_addr

From: Dmitry Vyukov
Date: Mon Mar 07 2016 - 14:56:41 EST

I kept the patch applied.

On Mon, Mar 7, 2016 at 8:51 PM, Marcelo Ricardo Leitner
<marcelo.leitner@xxxxxxxxx> wrote:
> On Mon, Mar 07, 2016 at 08:45:20PM +0100, Dmitry Vyukov wrote:
>> Yes, it is. I never saw this bug again. Forgot to update this thread. Sorry.
>
> Cool, thanks. The patch isn't applied yet, so either some other patch
> fixed it and this patch not necessary anymore or you kept the patch
> applied. Please confirm which one :-)
>
>> On Mon, Mar 7, 2016 at 8:44 PM, Marcelo Ricardo Leitner
>> <marcelo.leitner@xxxxxxxxx> wrote:
>> > On Tue, Jan 26, 2016 at 02:28:48PM +0100, Dmitry Vyukov wrote:
>> >> On Mon, Jan 25, 2016 at 6:52 PM, Marcelo Ricardo Leitner
>> >> <marcelo.leitner@xxxxxxxxx> wrote:
>> >> > Great. Dmitry, please give this a run. Local tests looked good but who
>> >> > knows what syzkaller may find.
>> >>
>> >> Now running with this patch.
>> >
>> > Hi Dmitry, do you remember if this one succeeded?
>> >
>> >> > Thanks
>> >> >
>> >> > --8<--
>> >> >
>> >> > Dmitry reported that sctp_add_bind_addr may read more bytes than
>> >> > expected in case the parameter is a IPv4 addr supplied by the user
>> >> > through calls such as sctp_bindx_add(), because it always copies
>> >> > sizeof(union sctp_addr) while the buffer may be just a struct
>> >> > sockaddr_in, which is smaller.
>> >> >
>> >> > This patch then fixes it by limiting the memcpy to the min between the
>> >> > union size and a (new parameter) provided addr size. Where possible this
>> >> > parameter still is the size of that union, except for reading from
>> >> > user-provided buffers, which then it accounts for protocol type.
>> >> >
>> >> > Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
>> >> > Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
>> >> > ---
>> >> > include/net/sctp/structs.h | 2 +-
>> >> > net/sctp/bind_addr.c | 14 ++++++++------
>> >> > net/sctp/protocol.c | 1 +
>> >> > net/sctp/sm_make_chunk.c | 2 +-
>> >> > net/sctp/socket.c | 5 +++--
>> >> > 5 files changed, 14 insertions(+), 10 deletions(-)
>> >> >
>> >> > diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
>> >> > index 20e72129be1ce0063eeafcbaadcee1f37e0c614c..97ba8a8c466f5c50bdc87ec578792e56553baa91 100644
>> >> > --- a/include/net/sctp/structs.h
>> >> > +++ b/include/net/sctp/structs.h
>> >> > @@ -1099,7 +1099,7 @@ int sctp_bind_addr_dup(struct sctp_bind_addr *dest,
>> >> > const struct sctp_bind_addr *src,
>> >> > gfp_t gfp);
>> >> > int sctp_add_bind_addr(struct sctp_bind_addr *, union sctp_addr *,
>> >> > - __u8 addr_state, gfp_t gfp);
>> >> > + int new_size, __u8 addr_state, gfp_t gfp);
>> >> > int sctp_del_bind_addr(struct sctp_bind_addr *, union sctp_addr *);
>> >> > int sctp_bind_addr_match(struct sctp_bind_addr *, const union sctp_addr *,
>> >> > struct sctp_sock *);
>> >> > diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
>> >> > index 871cdf9567e6bc9c13cb1077dc6866a67e6e4367..80129d10a0af9c33e7348b79d010b9e5e948e584 100644
>> >> > --- a/net/sctp/bind_addr.c
>> >> > +++ b/net/sctp/bind_addr.c
>> >> > @@ -111,7 +111,8 @@ int sctp_bind_addr_dup(struct sctp_bind_addr *dest,
>> >> > dest->port = src->port;
>> >> >
>> >> > list_for_each_entry(addr, &src->address_list, list) {
>> >> > - error = sctp_add_bind_addr(dest, &addr->a, 1, gfp);
>> >> > + error = sctp_add_bind_addr(dest, &addr->a, sizeof(addr->a),
>> >> > + 1, gfp);
>> >> > if (error < 0)
>> >> > break;
>> >> > }
>> >> > @@ -150,7 +151,7 @@ void sctp_bind_addr_free(struct sctp_bind_addr *bp)
>> >> >
>> >> > /* Add an address to the bind address list in the SCTP_bind_addr structure. */
>> >> > int sctp_add_bind_addr(struct sctp_bind_addr *bp, union sctp_addr *new,
>> >> > - __u8 addr_state, gfp_t gfp)
>> >> > + int new_size, __u8 addr_state, gfp_t gfp)
>> >> > {
>> >> > struct sctp_sockaddr_entry *addr;
>> >> >
>> >> > @@ -159,7 +160,7 @@ int sctp_add_bind_addr(struct sctp_bind_addr *bp, union sctp_addr *new,
>> >> > if (!addr)
>> >> > return -ENOMEM;
>> >> >
>> >> > - memcpy(&addr->a, new, sizeof(*new));
>> >> > + memcpy(&addr->a, new, min_t(size_t, sizeof(*new), new_size));
>> >> >
>> >> > /* Fix up the port if it has not yet been set.
>> >> > * Both v4 and v6 have the port at the same offset.
>> >> > @@ -291,7 +292,8 @@ int sctp_raw_to_bind_addrs(struct sctp_bind_addr *bp, __u8 *raw_addr_list,
>> >> > }
>> >> >
>> >> > af->from_addr_param(&addr, rawaddr, htons(port), 0);
>> >> > - retval = sctp_add_bind_addr(bp, &addr, SCTP_ADDR_SRC, gfp);
>> >> > + retval = sctp_add_bind_addr(bp, &addr, sizeof(addr),
>> >> > + SCTP_ADDR_SRC, gfp);
>> >> > if (retval) {
>> >> > /* Can't finish building the list, clean up. */
>> >> > sctp_bind_addr_clean(bp);
>> >> > @@ -453,8 +455,8 @@ static int sctp_copy_one_addr(struct net *net, struct sctp_bind_addr *dest,
>> >> > (((AF_INET6 == addr->sa.sa_family) &&
>> >> > (flags & SCTP_ADDR6_ALLOWED) &&
>> >> > (flags & SCTP_ADDR6_PEERSUPP))))
>> >> > - error = sctp_add_bind_addr(dest, addr, SCTP_ADDR_SRC,
>> >> > - gfp);
>> >> > + error = sctp_add_bind_addr(dest, addr, sizeof(addr),
>> >> > + SCTP_ADDR_SRC, gfp);
>> >> > }
>> >> >
>> >> > return error;
>> >> > diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
>> >> > index ab0d538a74ed593571cfaef02cd1bb7ce872abe6..2fb609008311f51344704d82f21b4de9f08253da 100644
>> >> > --- a/net/sctp/protocol.c
>> >> > +++ b/net/sctp/protocol.c
>> >> > @@ -214,6 +214,7 @@ int sctp_copy_local_addr_list(struct net *net, struct sctp_bind_addr *bp,
>> >> > (copy_flags & SCTP_ADDR6_ALLOWED) &&
>> >> > (copy_flags & SCTP_ADDR6_PEERSUPP)))) {
>> >> > error = sctp_add_bind_addr(bp, &addr->a,
>> >> > + sizeof(addr->a),
>> >> > SCTP_ADDR_SRC, GFP_ATOMIC);
>> >> > if (error)
>> >> > goto end_copy;
>> >> > diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
>> >> > index 5d6a03fad3789a12290f5f14c5a7efa69c98f41a..1b91e9760fe514db6d89457e1d5da9e02800745e 100644
>> >> > --- a/net/sctp/sm_make_chunk.c
>> >> > +++ b/net/sctp/sm_make_chunk.c
>> >> > @@ -1830,7 +1830,7 @@ no_hmac:
>> >> > /* Also, add the destination address. */
>> >> > if (list_empty(&retval->base.bind_addr.address_list)) {
>> >> > sctp_add_bind_addr(&retval->base.bind_addr, &chunk->dest,
>> >> > - SCTP_ADDR_SRC, GFP_ATOMIC);
>> >> > + sizeof(chunk->dest), SCTP_ADDR_SRC, GFP_ATOMIC);
>> >> > }
>> >> >
>> >> > retval->next_tsn = retval->c.initial_tsn;
>> >> > diff --git a/net/sctp/socket.c b/net/sctp/socket.c
>> >> > index 5ca2ebfe0be83882fcb841de6fa8029b6455ef85..213be3821a1d49e0c469c4ad4e9ff055a03205c5 100644
>> >> > --- a/net/sctp/socket.c
>> >> > +++ b/net/sctp/socket.c
>> >> > @@ -386,7 +386,8 @@ static int sctp_do_bind(struct sock *sk, union sctp_addr *addr, int len)
>> >> > /* Add the address to the bind address list.
>> >> > * Use GFP_ATOMIC since BHs will be disabled.
>> >> > */
>> >> > - ret = sctp_add_bind_addr(bp, addr, SCTP_ADDR_SRC, GFP_ATOMIC);
>> >> > + ret = sctp_add_bind_addr(bp, addr, af->sockaddr_len,
>> >> > + SCTP_ADDR_SRC, GFP_ATOMIC);
>> >> >
>> >> > /* Copy back into socket for getsockname() use. */
>> >> > if (!ret) {
>> >> > @@ -576,7 +577,7 @@ static int sctp_send_asconf_add_ip(struct sock *sk,
>> >> > addr = addr_buf;
>> >> > af = sctp_get_af_specific(addr->v4.sin_family);
>> >> > memcpy(&saveaddr, addr, af->sockaddr_len);
>> >> > - retval = sctp_add_bind_addr(bp, &saveaddr,
>> >> > + retval = sctp_add_bind_addr(bp, &saveaddr, sizeof(saveaddr),
>> >> > SCTP_ADDR_NEW, GFP_ATOMIC);
>> >> > addr_buf += af->sockaddr_len;
>> >> > }
>> >> > --
>> >> > 2.5.0
>> >> >
>> >> --
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